Bicycles have long been used as a means of transportation and recreation. However, until recently, virtually all practical bicycles have involved a relatively rigid frame, which transmits directly to the rider shocks resulting from potholes, rocks or other unevenness in the riding surface. This has resulted in discomfort to the rider which is at the least undesirable, if not unacceptable.
Recently, various bicycles have been introduced which provide some rear suspension, particularly for use with mountain bikes. Mountain bikes, because they are designed for use on rough terrain, are particularly susceptible to problems resulting from encounters with boulders, ditches, ruts, rocks, gravel, and other debris. Bicycles which provide a rear suspension solve a significant portion of the problem, and provide a greatly worthwhile improvement over the conventional, rigid frame mountain bike.
However, there remains a need for a front suspension capable of absorbing shocks while at the same time providing continuous control so that the rider can properly maneuver the bicycle at all times. Two factors figure prominently in the maintenance of control by the rider. The first is stiction, which basically refers to how well the front portion of the frame can absorb shocks. Obviously, a conventional rigid frame has little ability to absorb shocks, and so the rider has to adjust or otherwise accommodate unevenness in the riding surface. The second factor is trail. Trail refers to the distance, measured at the ground, between the center point of the hub of the front wheel, projected perpendicularly onto the ground, and the projection of the center line of the head of the frame along the head angle onto the ground.
The typical solution to this problem found in the prior art has been to include a shock absorber substantially like those provided on motorcycles, although with slightly different damping materials. Such shock absorbers are typically of the telescoping type. One current example of such a product is sold under the trademark "Rock Shox". The difficulty with such designs is that, while they can absorb small shocks, they have limited travel and are more prone to loss of control than is desirable, particularly upon hitting a larger obstacle such as a curb.
Another limitation with prior designs for front suspensions is that trail varies significantly with the amount of travel of the shock. In motorcycles such variation is not necessarily significant to the rider. However, in bicycles, which are much lighter weight than motorcycles, even slight variations--on the order of one-eighth inch--in trail can be detected by experienced riders, and modest variations of as little as one-half inch can make very significant differences. As a result, there has been a need for a bicycle front suspension which provides shock absorption without material variation in trail.
A further limitation with prior designs for front suspensions is that the fork assembly is created using a good amount of hand work and welding. This practice produces a fork structure which has weak points and also makes it difficult to maintain uniformly close tolerances between each front suspension. Further, excessive hand work is costly in terms of manhours and production quantities.
There has therefore been a need for a front suspension for a bicycle which is capable of encountering relatively large obstacles and absorbing the impact caused thereby while at the same time permitting the rider readily to retain control of the bicycle.